Bioethanol has a problem of consuming a large amount of energy for ethanol enrichment and distillation-purification since an automobile fuel requires high concentration ethanol of 99.5% by weight or more.
An SOFC system is equipped with a reforming device that vaporizes and reforms an ethanol aqueous solution of from 25 to 35% by weight to generate hydrogen gas, and an SOFC that generates electric power with the hydrogen gas, and thus does not require a distillation-purification column.
Under the circumstances, some proposals have been made for a system that intends to reduce the consumption energy cost and the equipment cost by combining a bioethanol producing device and an SOFC.
For example, PTL 1 proposes a combined system equipped with a means for withdrawing water-containing ethanol vapor having a concentration of from 30 to 70% by weight from an overhead of a distillation column of a bioethanol producing device, and a reforming means for producing a reformed gas from the overhead vapor, and also equipped with a SOFC operated with the reformed gas as a fuel.
PTL 2 describes a fuel cell system having a reforming device forming a reformed gas containing hydrogen from a hydrocarbon raw material supplied through reformation reaction including steam reformation reaction, a fuel cell performing electric power generation by supplying the reformed gas to an anode, and an anode off-gas introducing means for introducing at least a part of an anode off-gas containing water formed in association with the electric power generation to an inlet port of the reforming device through an ejector.
PTL 3 describes a fuel cell electric power generation system performing electric power generation in such a manner that an ethanol fuel having a concentration of from 15.4 to 46% by weight obtained from an ethanol fermented liquid is vaporized to form a mixed gas of steam and ethanol, which is reformed by being supplied to a reformation reaction zone to generate a reformed gas containing hydrogen, and the reformed gas is supplied to an SOFC.
NPL 1 reports a study on a method for providing a hydrogen rich gas suitable for supplying to a fuel cell, through steam reformation of bioethanol, in which FIG. 1 shows an electric power generation system having a step of providing a water-containing ethanol vapor of from 45 to 55% by weight through distillation of an ethanol fermented liquid, a step of reforming the water-containing ethanol vapor to form a reformed gas containing hydrogen, and a step of performing electric power generation with a fuel cell using the reformed gas as a fuel, and also shows that the heat of the off-gas discharged from the fuel cell is sent to and utilized in the distillation step and the reformation step.